Vibration resistant switch utilizing an elongated stationary contact co-acting with a planar movable apertured contact



March 18, 1969 Hu g so ET AL 3,433,912

VIBRATION RESISTANT SWITCH UTILIZING AN ELONGATED STATIONARY CONTACT (IO-ACTING WITH A PLANAR MOVABLE APERTURED CONTACT Filed D60. 20, 1966 United States Patent Oflice 3,433,912 Patented Mar. 18, 1969 54,459/ 65 US. Cl. 200-83 Int. Cl. H01h 35/34 7 Claims ABSTRACT OF THE DISCLOSURE A vibration resistant electric switch comprising an elongated contact adapted to be forcibly inserted into an aperture in a co-operating contact of planar form, the planar contact being provided with slits extending outwardly from the aperture therein so as to provide two or more fingers which resiliently engage the sides of the elongated contact when it is forced into the aperture.

This invention relates to electric switches.

It is an object of the present invention to provide an electric switch having at least one pair of contacts which, once engaged, will remain engaged when subject to severe vibrational forces.

According to the present invention an electric switch incorporates at least one pair of contacts which are adapted to engage in operation of the switch, one of the contacts being in the form of an elongated member and the other contact being in the form of a planar member formed of resilient material and having an aperture in which said elongated member is inserted when the switch is operated, the cross-sectional areas of the elongated member and the aperture being such that when the elongated member is inserted in the aperture, at least part of the edge of the aperture in the planar member forcibly engages the side of the elongated member.

Preferably the planar member is provided with at least two slits extending outwardly from the aperture so as to provide at least two resilient fingers which bend when the elongated member is inserted in the aperture, thereby forcibly engaging the side of the elongated member.

In one particular arrangement in accordance with the invention an electric switch includes two pairs of contacts as described in either of the preceding paragraphs, the two elongated members constituting fixed contacts to which leads may be connected and the two planar members constituting movable contacts and being electrically connected together, thereby to provide an electrical connection between the two leads when the switch is operated.

One electric switch in accordance with the invention will now be described, by way of example, with reference to the drawing accompanying the Provisional Specification in which:

FIGURE 1 is a sectional view of the switch in its unoperated condition;

FIGURE 2 is an end view of the switch;

FIGURE 3 is an enlarged perspective view of a part of the switch; and

FIGURE 4 is a fragmentary sectional view of a part of the switch in its operated condition.

Referring to FIGURES 1 and 2, the switch incorporates a housing including a short generally cylindrical member 1 made of thermoplastic material in which is formed a cylindrical recess 2 of rectangular cross-section which extends into the member 1 from one of its end faces, the

recess 2 having a depth equal to about half the axial length of the member 1. A small circular aperture ,3 extends centrally into the member 1 from its other end face, and a corresponding aperture 4 is formed centrally in the base of the recess 2, the adjacent ends of the apertures 3 and 4 being separated by a thin membrane 5 of thermoplastic material formed integrally with the member 1. In the base of the recess 2, at equally spaced positions around the aperture 4 there are embedded four gold plated brass members 6 which constitute the fixed contacts of the switch. Each of the members 6 is in the form of a rod provided with an outwardly extending flange 7 half way along its length, each of the flanges 7 being disposed with one main face in the plane of the base of the recess 2 so that one end of each of the members 6 projects into the recess 2 and the remainder of each member 6 is embedded in the thermoplastic material. The part of the members 6 projecting into the recess 2 are each of diameter 0.051 inch and are pointed at their free ends. The embedded end of each of the members 6 is soldered to one end of a separate lead 8 which is also embedded in the thermoplastic material, the leads 8 being brought together into a sleeving 9 where they leave the member 1.

In manufacture of the member 1, the contacts 6 with the leads 8 attached are set up in a jig and the member 1 is moulded around the contacts 6 and leads 8.

The housing further includes a stainless steel circular disc 10 which is secured by means of four bolts 11 to the end of the member 1 from which the recess 2 extends. A circular aperture 12 extends centrally through the disc 10 and a shallow dish-shaped recess 13 extends into the disc 10 from its main face remote from the member 1. The housing is completed by a stainless steel hexagonal cap 14 which screws onto a thread provided on the external curved surface of the disc 10, the cap 14 having a circular aperture 15 extending axially through it.

Between the adjacent surfaces of the cap 14 and the disc 10 there is clamped a thin circular stainless steel diaphragm 16, the joint between the cap 14 and the diaphragm 16 being made airtight by means of a rubber sealing ring 25 which clamps between the cap 14 and the diaphragm 16 and is located in an annular groove formed in the cap 14.

In the compartment formed by the disc 10 and the recess 2 is housed a plunger 17 formed of thermoplastic material which carries the moving contacts of the switch.

Referring now to FIGURE 3, the plunger 17 comprises a flat rectangular planar portion 18- from the centre of each main face of which there projects a short stub 19 of circular cross-section; in addition, four circular apertures 20 extend through the portion 18, the apertures being at equally spaced positions around the centre of the portion 18. The moving contacts are constituted by two planar members 21 formed from 0.003 inch thick beryllium copper strip gold plated to a depth of at least 0.0001 inch. Each of the members 21 is of substantially figure eight shape, and through each end of each member 21 there extends centrally an aperture 22 of equilateral triangular shape from each of the apices of which a slit 23 extends outwardly. Each of the slits 23 has a width of .012 inch and extends to a point 0.100 inch from the centre of the associated aperture 22, and the three straight edges of each aperture 22 are each at a perpendicular distance of 0.02 inch from the centre of that aperture 22.

The two moving contacts 21 are embedded in the planar portion 18 of the plunger 17 so as to lie side by side, but insulated from one another, and in a plane parallel to the main faces of the planar portion 18 with each of the apertures 22 aligned coaxially with a different one of the apertures 20.

Referring again to FIGURE 1, in the unoperated condition of the switch the plunger 17 fits in the compartment formed by the disc 10 and the recess 2 with one of the main faces of the planar portion 18 of the plunger 17 in contact with the disc 10, with the stub 19 projecting from that main face of the planar portion 18 located in the aperture 12 in the disc 10, and with the free end of this stub 19 in contact with the diaphragm 16. The other stub 19 locates in the aperture 4 with its free end closely adjacent the membrane 5.

The recess 2 also houses a rectangular piece of polyester film 24 disposed between the plunger 17 and the fixed contacts 6 and having a central aperture through which the stub 19 fits.

To operate the switch a high pressure air supply is connected to the outer end of the aperture 15 in the cap 14. The pressure of the air causes the diaphragm 16 to be deflected and mould itself to the wall of the recess 13 in the disc 10. In so doing the diaphragm 16 pushes the plunger 17 towards the other end of the recess 2, causing the membrane to break and the parts of the fixed contacts 6 projecting into the recess 2 to be forced through the polyester film 24 and into the apertures 22 in the moving contact members 21, thereby connecting the leads 8 together in pairs. As a result, the three triangular metal fingers between adjacent pairs of the slits 23 in each moving contact member 21 are flexed so that their inner ends forcibly engage the side of the corresponding fixed contact 6', thereby rendering withdrawal of the moving contacts 21 from the fixed contacts 6 very difficult (see FIGURE 4). Electrical connections secure against vibrational stresses are thus obtained between the leads 8-.

It will be appreciated that the provision of the membrane 5 and the polyester film 24 serves to prevent accidental operation of the switch.

We claim:

1. An electric switch comprising at least one pair of contacts which are adapted to engage in operation of the switch, one of the contacts being in the form of an elongated member and the other contact being in the form of a thin planar member formed of resilient material and having an aperture formed in it, and means for forcibly inserting the elongated member into said aperture when the switch is operated, the planar member being provided with at least two slits extending outwardly from the aperture so as to provide at least two resilient fingers which bend when the elongated member is inserted in the aperture, thereby forcibly engaging the side of the elongated member.

2. A switch according to claim 1 wherein the elongated member is of circular cross-section, the aperture in the planar member is of equilateral triangular cross-section, a slit extends outwardly from each of the apices of the aperture, and the radius of the elongated member is slightly greater than the perpendicular distance of the edges of the aperture from the centre of the aperture.

3. A switch according to claim 1 wherein the switch incorporates a housing which provides a cylindrical compartment into which the elongated member projects perpendicularly from one end, the planar member being disposed in said compartment in a plane parallel to the ends of the compartment, and said means for forcibly inserting the elongated member into the aperture in the planar member comprises means for moving the planar member axially along said compartment towards the elongated member.

4. A switch according to claim 3 wherein said planar member is moved pneumatically.

5. A switch according to claim 3 wherein the planar member is mounted on a carrier member provided with a stub which locates in an aperture provided in the end of the compartment from which the elongated member projects.

'6. A switch according to claim 5 wherein a membrane extends across the aperture in which said stub locates, the membrane requiring to be pierced by the stub before the contacts can be brought into engagement thereby, reducing the likelihood of accidental operation of the switch.

7. A switch according to claim 3 including two said contacts in the form of elongated members to which leads may be connected and including two said contacts in the form of aperture planar members which are electrically connected together, thereby to provide an electrical connection between the two leads when the switch is operated.

References Cited UNITED STATES PATENTS 1,356,909 10/1920 Delaney 200-442 FOREIGN PATENTS 921,463 1/1947 France.

ROBERT K. SCHAEFER, Primary Examiner.

H. BURKS, Assistant Examiner.

U.S. Cl. X.R. 200142 

